<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        
    </style>
</head>
<body>
    
</body>
<script>

    console.log( 0.1 + 0.2 === 0.3 );
    console.log( 0.1 + 0.2 );
    console.log( (0.1 + 0.7) );
    console.log( (0.1 + 0.7).toFixed(1) );
    console.log( (0.1 + 0.7).toFixed(5) );

    // 主动保留n位小数

</script>
</html>